In the field of toners for electrophotography, with the progress of electrophotographic systems, it has been demanded to develop toners adaptable for high image quality and high copying speed. From the viewpoint of the high image quality, the toners have been required to have a small particle size. Thus, there has been proposed a so-called chemical toner obtained by a chemical method such as a polymerization method and an emulsification and dispersion method in place of the conventional melt-kneading and pulverizing method. The chemical toner has been noticed from the viewpoints of a small particle size and a narrow particle size distribution thereof.
The toner obtained by the melt-kneading and pulverizing method is readily electrically charged owing to its irregular shape having concave and convex portions. However, the toner obtained by the chemical method have substantially no charge-generating portions by itself owing to a spherical shape thereof. Therefore, it is required to allow a charge control agent to exist on a surface of the toner.
Thus, as such a toner on the surface of which a charge control agent is present, there is disclosed a toner obtained by mixing a dispersion of resin particles enclosing a charge control agent with emulsified particles having an average particle size of about 8 μm and then drying the resultant mixture (JP 10-293419A).
Also, as the toner containing core particles produced by an emulsification aggregating method onto which a charge control agent adheres, there are disclosed a toner obtained by forming aggregated particles in a dispersion containing resin particles, producing coalesced particles therefrom, and then adding styrene-acryl resin particles enclosing a charge control agent to the coalesced particles (JP 2002-82490A); a toner obtained by adding a charge control agent during a period between initiation and termination of a step of forming aggregated particles in a dispersion containing resin particles (JP 2000-347449A); and a toner obtained by forming aggregated particles in a dispersion containing resin particles, allowing particles of a charge control agent and a styrene-acryl resin to adhere onto the aggregated particles, and heating the resultant particles to produce coalesced particles (JP 2000-267348A).
In addition, there has been reported a toner obtained by mixing toner mother particles (core particles) and a charge control agent with each other (JP 2002-357929A).